Just a suggestion for you ..... if you decide to buy an LPM, and sell certified output lasers, please do the measures in the right way .....
I'm NOT try to bash you, but, i have seen on the internet some companies that sell lasers, and post pictures with a LPM, for show that their lasers are the power that they say, and some (luckily not all) of them, do this in the worse way ..... where, as example, you can see that a measure is taken with the laser in contact with the thermopile head, when almost all knows that a thermopile is so sensitive that, in this way, you measure also the heat of the laser module as output power .....
A good way for measure the effective power of a laser, is to check the zero set of the LPM just before each reading, to keep the laser at least at 20cm away from the reading head (40cm is usually a good distance), and, in case of a focusable laser, to slightly de-focus the beam, so it cover approximatively half of the reading surface, and always keeping it centered (cause, for their nature, the thermopiles reads always more of the real value, if the beam is pointed focused near the border of the reading disk)
Doing the measure in this way, you know the real output power of your lasers ..... and about IR filtering, only the worse DPSS modules have more IR than green, usually a decent module have around 15 to 20% of the output power as IR (if unfiltered), and some good ones can have less than 10% of IR in the green ..... this can help you also in discarding very low quality manufacturers, by the way .....
Anyway, for have a good "tools set", just get an anti-IR filter, with the LPM, so you can read the laser directly, and then place the filter in front of it, and see how much it decrease ..... an advice, also the green light is a little bit attenuated, from the IR filter (there is always a loss of power, when a laser beam pass through an object, also if it was pure transparent glass, cause there are always some reflections and refractions) ..... If you decide to buy a professional IR filter, they are available with AR coating, and usually the seller gives also attenuation graphics, so one can directly know the loss of the green component of the beam ..... but they are, usually, not cheap .....
If instead you decide to use a normal, uncoated IR filter, you need to do a simple test, for know how much, in percentage, it take away from your green light ..... the easiest system is to get two filters, stick one on a green laser, and take the power measure with it (so the measured light is practically almost all green, with no IR) ..... then, mounting the second on a stand (preferably a slightly angled, respect the perpendicular), and place it in the beam, reading the new value ..... the difference between the 2 values is the percentage of green that the filter take away, at that angle, so when you place it in the path of an unfiltered laser, you know how much percent of green it read less than the real, after having filtered out the IR .....
Let me give an example with numbers, cause my English is not the best
..... suppose that you read the IR filtered laser at 100mW ..... and placing the second filter in the beam path, your reading becomes 95mW ..... then you know that your filter, other than the IR, take away also 5% of the green part ..... so, when you read an unfiltered laser, and read, say, 200mW, then place this filter in the beam path and read, say, 140mW, the real power of the green light is 140, plus the 5% took out from the filter (7mW), that make 147mW .....